1. Field of the Invention
The invention is in the field of industrial burners and incinerators and, more particularly, relates to new industrial burners for combustion of particulate fuels such as wet or dry sawdust and many types of varying moisture content biomass fuels including, agricultural products, wood waste, bagasse, poultry waste, and other cellulosic materials, and especially in the wood products manufacturing or processing operations, including combustion of smoke or other combustible gases produced by processes relating to such products and other gases, such as industrial off-gases, and specifically operating with high turndown ratios and high heat release ratios.
2. Related Art
In the general field of burners and incinerators for industrial purposes, there are myriad different configurations, wherein there has for many years been an increasing focus on efficiency and output. Thus, there have been proposals for swirling or cyclonic combustion and combustion chambers of unusual geometries, as well as many proposals for controlling the entry of air and fuel into the combustion chamber for contributing to swirling or other patters of combustion motion. There have been various burners proposed for burning, as feed stocks, organics or biomass materials, including so-called green (high moisture content) sawdust, solid cellulosic or wood-containing waste, waste wood, and fragments of wood, and all of which may herein be referred to as wood products.
In burners useful for burning such materials, there has been insufficient emphasis on achieving efficiency and flexibility which can result from achieving a high turndown ratio (which may for convenience be abbreviated "TDR"). Turndown ratio is the maximum firing rate of the burner divided by the minimum firing rate of the burner. Prior constructions have not achieved sufficiently high TDRs.
The provision of a high TDR for a burner capable of carrying out combustion of wood products is highly desirable, as such a burner would be capable of being operated over a great dynamic range. If, for example, in a manufacturing or materials handling operation which creates such wood products, which are to be combusted (as for heating or energy extraction for other processes or purposes), the use of a burner having a limited TDR can require that burner operation be terminated if wood product supply rates are insufficient to achieve the minimum firing rate of the burner. Or, if combustion of wood products at low feed rates is to be carried out, an auxiliary fuel such as natural gas, liquefied petroleum (LP) gas, propane, or fuel oil, may have to be fed into the burner for maintaining combustion. But, on the other hand if the burner is designed for burning wood products at low feed rates, its output may be insufficient to handle high feed rates when wood products to be combusted are being produced at high volumes. Further, if TDR can be increased, much less auxiliary fuel will be required to initiate burner operation.
As an example, in a wood products manufacturing or processing operations, very substantial quantities of green sawdust are created during sawing, planing, shaping, etc., but the rate of production of sawdust will be dependent upon the various wood-handling processes, which vary in rate, time of operation, and volume, so that sawdust may be produced at a highly variable rate.
If the sawdust is to be combusted by a burner for the purpose of extracting heat for other uses (such as heating, boiler operation, drying, etc.), the use of a burner having a high TDR enables its operation on continuous basis or at least for longer periods of operation, as desired.
In the wood products industry, as including also the production of charcoal, there is a need also for dealing with smoke and other gases produced during operations. For example, in cooperage operations where barrels are produced for aging of beverages, such as wines or brandies, etc., some types of barrels require that they be charred, as for the aging of various kinds of whiskeys. Charring operations produce smoke which may need to be combusted. So also, in charcoal kilns, the off-gases are sources of environmental pollution, and may also need to be combusted, i.e., by oxygenation combustion.
It would be desirable to combine a burner, capable of burning wood products for the above-noted purposes, with features for combustion of off-gases in the wood products industry.
Present burners in the wood products industries have not met the needs for these kinds of combustion, and have not achieved satisfactory TDR and efficiencies for acceptable usage in the wood products industries.